PAM8404 3W/CH Filterless Stereo Class-D Audio Amplifier Features Description n 3W Output at 10% THD with a 4 Ω Load and 5V Supply n Supply Voltage from 2.5V to 5.5 V n Efficiency Up to 89% n Superior Low Noise without Input n Few External Components to Save the Space and Cost n Short Circuit Protection n Thermal Shutdown n Space Saving Packages : 2mm X 2mm WCSP 4mm X 4mm Thin QFN n Pb-Free Packages The PAM8404 is a 3W high efficiency filterless class-D audio amplifier in 4mmX4mm QFN and 2mmX2mm wafer chip scale (WCSP) packages that requires few external components. Features like 89% efficiency, -63dB PSRR, improved RF-rectification immunity, and very small PCB area make the PAM8404 class-D amplifier ideal for cellular handset and PDA applications. In cellular handsets, the earpiece, speaker phone, and melody ringer can each be driven by the PAM8404 . The PAM8404 allows independent gain by summing signals from seperate sources, and has as low as 43 μ V A-weighted noise floor. Applications n n n n n LCD Monitor / TV Projector Notebook Computers Portable Speakers Portable DVD Players, Game Machines Cellular Phones/Speaker Phones PAM8404 is available in QFN 4mmx4mm and WCSP 2mmx2mm packages. Typical Application Circuit VDD 10μF 1μF PVDD PGND Radiated Emissions 0.22μF INR+ OUTR+ INR+ INR- INR0.22μF OUTR- FCC Class B Limit ON SDR OFF G1 G1 G0 G0 PAM8404 ON SDL OFF 0.22μF INL+ OUTL+ INL+ INL- OUTL- INL0.22μF AVDD AGND 1μF VDD 10μF Power Analog Microelectronics , Inc www.poweranalog.com 03/2009 Rev 1.1 1 PAM8404 3W/CH Filterless Stereo Class-D Audio Amplifier Block Diagram V DD To Battery CS OUTR+ INR+ Gain Adjust + - + PAM Modulation HBridge OUTR- INR- GND Internal Oscillator OUTL+ INL+ Gain Adjust + - + PAM Modulation HBridge INL- OUTL- G0 G1 Short-Circuit Protection SDR 300kΩ Bandgap OTP SDL 300kΩ Power Analog Microelectronics , Inc www.poweranalog.com 03/2009 Rev 1.1 2 PAM8404 3W/CH Filterless Stereo Class-D Audio Amplifier Pin Configuration & Marking Information QFN 4mmx4mm Top View INL+ PVDD OUTL+ OUTL- 20 19 18 17 16 INR+ A4 INR- A3 AGND A2 INL- A1 INL+ WCSP 2mmx2mm Top View 1 G1 AVDD OUTR+ 2 OUTL+ 3 PVDD PGND OUTR- OUTR+ 14 P8404 XXXYW PVDD 13 4 PGND PGND 12 5 OUTL- OUTR- 11 FR YW NC AGND G0 SDL AVDD INR+ SDR SDR D1 INR- G1 SDL C1 INL- NC B1 G0 15 6 7 8 9 10 FR: Product Code of PAM8404 X: Internal Code Y: Year W: Week (Marking) Pin Descriptions Name G1 Pin Number 1 B2 Description Gain select (MSB) OUTL+ 2 A3 Left channel positive differential output PVDD 3,13 A2 Power supply (must be same voltage as AVDD) PGND 4,12 C4 Power ground OUTL- 5 A4 Left channel negative differential output NC 6,10 - SDL 7 B4 Left channel shutdown terminal (active low) SDR 8 B3 Right channel shutdown terminal (active low) AVDD 9 D2 Analog supply (must be same voltage as PVDD) OUTR- 11 D4 Right channel negative differential output OUTR+ 14 D3 Right channel positive differential output G0 15 C2 Gain select (LSB) INR+ 16 D1 Right channel positive input INR- 17 C1 Right channel negative input AGND 18 C3 Analog ground INL- 19 B1 Left channel negative input INL+ 20 A1 Left channel positive input No connect Power Analog Microelectronics , Inc www.poweranalog.com 03/2009 Rev 1.1 3 PAM8404 3W/CH Filterless Stereo Class-D Audio Amplifier Absolute Maximum Ratings These are stress ratings only and functional operation is not implied. Exposure to absolute maximum ratings for prolonged time periods may affect device reliability. All voltages are with respect to ground. Supply Voltage . ...........................................6.0V Input Voltage.............................-0.3V to V DD+0.3V Maximum Junction Temperature..................150°C Storage Temperature.....................-65 °C to 150 °C Soldering Temperature.................... 250°C,10 sec Recommended Operating Conditions Supply voltage Range........................ 2.5V to 5.5V Operation Temperature Range.........-40 °C to 85 °C Junction Temperature Range.........-40 °C to 125 °C Thermal Information Parameter Symbol Thermal Resistance (Junction to Ambient) θJA Thermal Resistance (Junction to Case) θJC Package Maximum WCSP2x2-16 64 QFN4x4-20 31 WCSP2x2-16 - QFN4x4-20 13 Unit °C/W °C/W Power Analog Microelectronics , Inc www.poweranalog.com 03/2009 Rev 1.1 4 PAM8404 3W/CH Filterless Stereo Class-D Audio Amplifier Electrical Characteristic QFN 4x4 20-Pin T A=25 °C, AVDD=PVDD=5V, GND=PGND=0V, unless otherwise noted. Parameter Supply Voltage Symbol Test Conditions VDD 2.5 THD+N=10% f=1kHz RL=4Ω THD+N=1% f=1kHz R L=4Ω Output Power PO THD+N=10% f=1kHz RL=8Ω THD+N=1% f=1kHz R L=8Ω VDD =5.0V,Po=0.5W,RL=8Ω Total Harmonic Distortion Plus Noise THD+N VDD =3.6V,Po=0.5W,RL=8Ω VDD =5.0V,Po=1W,R L=4Ω VDD =3.6V,Po=1W,R L=4Ω Power Supply Ripple Rejection Crosstalk Signal-to-noise ratio PSRR Cs SNR Dynamic range Vn Dyn Efficiency η Quiescent Current IQ Shutdown Current ISD Static Drain-to-source On-state Resistor Rdson VDD =5V 5.5 3 VDD =3.6V 1.5 VDD =5V 2.35 VDD =3.6V 1.2 VDD =5V 1.7 VDD =3.6V 0.9 VDD =5V 1.4 VDD =3.6V 0.7 f=1kHz f=1kHz 0.15 0.27 0.23 0.24 VDD =5.0V, Inputs ac-grounded with f=100Hz -48 Cin=1μF -63 f=1kHz V W W W W % % dB VDD =5V,Po=0.5W,R L=4Ω,Gv=23dB F=1kHz -93 dB VDD =5V, Vorms=1V,Gv=23dB A-weighting 87 dB A-weighting 43 BW 22Hz-22kHz No A-weighting 59 VDD =5.0V, THD=1% A-weighting 97 VDD =5V, Inputs ac-grounded with Output noise MIN TYP MAX UNIT Cin=1μF RL=8Ω, THD=10% RL=4Ω, THD=10% VDD =5V f=1kHz No load VDD =3.6V VDD =5.5V IDS=500mA,Vgs=5V 89 84 11 6 Vsd=0.3V <1 PMOS 250 NMOS 170 μV dB % mA μA mΩ Switching Frequency fsw VDD =3V to 5V 300 kHz Output Offset Voltage Vos Vin=0V, V DD =5V 10 mV closed-loop voltage gain Over Temperature Protection Gain VDD =5V RL=4Ω f=1kHz OTP G0=L G1=L 6 G0=H G1=L 12 G0=L G1=H 18 G0=H G1=H 24 150 No Load, Junction Temperature Over Temperature Hysterisis dB OTH °C 50 Power Analog Microelectronics , Inc www.poweranalog.com 03/2009 Rev 1.1 5 PAM8404 3W/CH Filterless Stereo Class-D Audio Amplifier Electrical Characteristic WCSP 2x2-16 T A=25 °C, AVDD=PVDD=5V, GND=PGND=0V, unless otherwise noted. Parameter Supply Voltage Symbol Test Conditions VDD 2.5 THD+N=10% f=1kHz RL=4Ω THD+N=1% f=1kHz RL=4Ω Output Power PO THD+N=10% f=1kHz RL=8Ω THD+N=1% f=1kHz RL=8Ω VDD =5.0V,Po=0.5W,RL =8Ω Total Harmonic Distortion Plus Noise THD+N VDD =3.6V,Po=0.5W,RL =8Ω VDD =5.0V,Po=1W,RL=4Ω VDD =3.6V,Po=1W,RL=4Ω Power Supply Ripple Rejection Crosstalk Signal-to-noise ratio PSRR Cs SNR VDD =5.0V, Inputs ac-grounded with Dynamic range Vn Dyn Efficiency η Quiescent Current IQ Shutdown Current ISD Static Drain-to-source On-state Resistor Rdson 5.5 VDD =5V 2.2 VDD =3.6V 1.2 VDD =5V 1.8 VDD =3.6V 1 VDD =5V 1.5 VDD =3.6V 0.8 VDD =5V 1.2 VDD =3.6V 0.6 f=1kHz f=1kHz 0.4 0.3 0.2 W W W W % % dB VDD =5V,Po=0.5W,RL=4Ω,Gv=23dB f=1kHz -70 dB VDD =5V, Vorms=1V,Gv=23dB A-weighting 85 dB A-weighting 34 BW 22Hz-22kHz No A-weighting 54 VDD =5.0V, THD=1% A-weighting 98 Cin=1μF RL=8Ω, THD=10% RL=4Ω, THD=10% VDD =5V f=217Hz 0.3 V -50 Cin=1μF VDD =5V, Inputs ac-grounded with Output noise MIN TYP MAX UNIT f=1kHz No load VDD =3.6V VDD =2.5V to 5.5V IDS=500mA,Vgs=5V 85 75 12 7 Vsd=0.3V <1 PMOS 500 NMOS 460 μV dB % mA μA mΩ Switching Frequency fsw VDD =5V 300 kHz Output Offset Voltage Vos Vin=0V, V DD =5V 20 mV closed-loop voltage gain Over Temperature Protection Gain VDD =5V RL=4Ω f=1kHz OTP G0=L G1=L 6 G0=H G1=L 12 G0=L G1=H 18 G0=H G1=H 24 150 No Load, Junction Temperature Over Temperature Hysterisis dB OTH °C 50 Power Analog Microelectronics , Inc www.poweranalog.com 03/2009 Rev 1.1 6 PAM8404 3W/CH Filterless Stereo Class-D Audio Amplifier Typical Operating Characteristics (T =25°C) A QFN 4x4 20-Pin Efficiency vs Output Power R L=8 Ω, V DD=5V, L =33 μ H 100 90 90 80 80 70 70 Efficiency(%) Efficiency(%) 100 Efficiency vs Output Power R L=4 Ω, V DD=5V, L =33 μ H 60 50 40 60 50 40 30 30 20 20 10 10 0 200 400 600 800 1000 1200 1400 1600 1800 0 300 600 900 1200 1500 1800 2100 2400 2700 3000 Output Pow er(mW) Output Pow er(mW) THD+N vs Output Power R L=4 Ω , Gain=23dB, f=1kHz THD+N vs Output Power R L=8 Ω , Gain=23dB, f=1kHz 30 30 VDD=5V VDD=5V 10 5 10 5 VDD=3.6V 2 2 VDD =2.5V 1 % VDD=3.6V VDD =2.5V 1 % 0.5 0.5 0.2 0.2 0.1 0.1 0.05 0.05 0.02 0.02 0.01 10m 20m 50m 100m 200m 500m 1 2 0.01 10 m 4 20 m 50 m 100m 30 20 200m 500m THD+N vs Frequency P O=0.5W, R L=8 Ω , C IN=1 μ F,Gain=23dB 30 20 10 10 5 5 2 % 2 4 VDD =3.6V 1 % 0.5 0.2 0.5 0.2 0.1 0.1 0.05 0.05 VDD =5V 0.02 0.01 20 2 THD+N vs Frequency P O=0.5W, R L=4 Ω , C IN=1 μ F,Gain=23dB VDD =3.6V VDD =5.5V 1 1 W W VDD =5V VDD =5.5V 0.02 50 100 200 500 1k 2k 5k 10k 0.01 20 20k Hz 50 100 200 500 1k 2k 5k 10k 20k Hz Power Analog Microelectronics , Inc www.poweranalog.com 03/2009 Rev 1.1 7 PAM8404 3W/CH Filterless Stereo Class-D Audio Amplifier Typical Operating Characteristics (T =25°C) A QFN 4x4 20-Pin THD+N vs Frequency V DD=5V, R L=4 Ω , C IN=1 μ F,Gain=23dB THD+N vs Frequency V DD=5V, R L=8 Ω , C IN=1 μ F,Gain=23dB 30 20 30 20 10 10 5 5 PO=1W 2 PO =1.3W 1 % PO=1W 2 1 % 0.5 0.2 PO=0.5W 0.5 0.2 PO=0.5W 0.1 0.1 0.05 0.05 0.02 0.02 0.01 20 50 100 200 500 1k 2k 5k 10k 0.01 20 20k PO =2W 50 100 200 Hz 500 1k 2k 5k 10k 20k 10 k 20 k Hz Frequency Response V DD=5V, R L=4 Ω , C IN=1 μ F +25 +0 PSSR vs Frequency Input ac-ground, V DD=5V 200mVpp, R L=4 Ω , C IN=1 μ F, gain=16dB G0=1G1=1 +22.5 -10 +20 -20 +17.5 A -30 G0=0 G1=1 d +15 B r +12.5 -40 d B G0=1G1=0 +10 R -50 -60 +7.5 -70 G0=0 G1=0 +5 -80 +2.5 -90 +0 20 50 100 200 500 1k 2k 5k L -100 20 10k 20k 50 100 200 1k 2k 5k Noise Floor FFT Inputs ac-ground, V DD=5V, C IN=1 μ F, R L=4 Ω , Gain=23dB Crosstalk vs Frequency V DD=5V, R L=4 Ω , Gain=23dB -65 500 Hz Hz -50 T T -70 -60 -75 -80 -70 R to L -85 d B d B r -90 -95 -80 L -90 A -100 -100 -105 -110 L to R -110 -115 -120 20 R 50 100 200 500 1k 2k 5k 10k -120 20 20k Hz 50 100 200 500 1k 2k 5k 10k 20k Hz Power Analog Microelectronics , Inc www.poweranalog.com 03/2009 Rev 1.1 8 PAM8404 3W/CH Filterless Stereo Class-D Audio Amplifier Typical Operating Characteristics (T =25°C) A QFN 4x4 20-Pin 16 Quiescent Current vs Supply Voltage No Input, R L=No Load Frequency vs Supply Voltage Input ac-ground 300 296 12 Frequency(KHz) Quiescent Current(mA) 14 10 8 6 4 292 288 284 2 0 280 2 2.5 3 3.5 4 4.5 5 5.5 6 2 2.5 3 Pow er Supply Voltage(V) 3.5 4 4.5 5 5.5 6 5.5 6 Pow er Supply Voltage(V) Output Power vs Supply Voltage C IN=1 μ F, R L=4 Ω , Gain=23dB, f=1kHz Output Power vs Supply Voltage C IN=1 μ F, R L=8 Ω , Gain=23dB, f=1kHz 4 2.5 3.5 3 Output Power(w) Output Power(w) 2 10% 1.5 1 1% 2.5 10% 2 1.5 1% 1 0.5 0.5 0 0 2 2.5 3 3.5 4 4.5 5 5.5 6 2 Pow er Supply Voltage(V) 2.5 3 3.5 4 4.5 5 Pow er Supply Voltage(V) Power Analog Microelectronics , Inc www.poweranalog.com 03/2009 Rev 1.1 9 PAM8404 3W/CH Filterless Stereo Class-D Audio Amplifier Typical Operating Characteristics (T =25°C) A WCPS 2x2-16 Efficiency vs Output Power R L=8 Ω, V DD=5V, L =22 μ H 100 80 90 70 80 Efficiency(%) Efficiency(%) 90 Efficiency vs Output Power R L=4 Ω, V DD=5V, L =22 μ H 60 50 40 70 60 50 40 30 30 20 20 10 10 0 200 400 600 800 1000 1200 1400 1600 0 300 600 Output Pow er(mW) 30 900 1200 1500 Output Pow er(mW) THD+N vs Output Power R L=4 Ω , Gain=23dB, f=1kHz THD+N vs Output Power R L=8 Ω , Gain=23dB, f=1kHz 30 20 VDD=5.5V 10 VDD=5.5V 10 VDD=5V 5 VDD=5V 5 % 1800 2100 2400 2 VDD =3.6V 1 VDD =3.6V 2 % 1 0.5 0.2 0.1 0.5 0.05 0.2 0.02 0.1 10m 20m 50m 100m 200m 500m 1 2 0.01 10m 4 20m 50m 100m W 30 20 10 10 5 5 1 % 0.5 0.2 4 VDD =3.6V 0.5 0.2 VDD =5V 0.1 0.05 0.02 0.02 50 100 200 500 Hz 1k 2k VDD =5V 0.1 0.05 0.01 20 2 VDD =5.5V 2 VDD =3.6V 1 % 1 THD+N vs Frequency P O=0.5W, R L=4 Ω , C IN=1 μ F,Gain=23dB 30 20 VDD =5.5V 500m W THD+N vs Frequency P O=0.5W, R L=8 Ω , C IN=1 μ F,Gain=23dB 2 200 m 5k 10k 0.01 20 20k 50 100 200 500 1k 2k 5k 10k 20k Hz Power Analog Microelectronics , Inc www.poweranalog.com 03/2009 Rev 1.1 10 PAM8404 3W/CH Filterless Stereo Class-D Audio Amplifier Typical Operating Characteristics (T =25°C) A WCPS 2x2-16 THD+N vs Frequency V DD=5V, R L=8 Ω , C IN=1 μ F, Gain=23dB 30 20 30 20 10 10 5 5 PO=1.2W PO =1 W 2 PO =1.8W 2 1 % THD+N vs Frequency V DD=5V, R L=4 Ω , C IN=1 μ F, Gain=23dB 1 % 0.5 0.5 0.2 0.2 0.1 0.1 PO=0.5W 0.05 0.05 0.02 0.02 0.01 20 50 100 200 500 1k 2k 5k 10k 0.01 20 20k PO=0.5W PO=1.2W 50 100 200 500 Hz Hz 1k 2k 5k 10k 20k 10k 20k PSSR vs Frequency Input ac-ground, V DD=5V 200mVpp, R =4 Ω , C IN=1 μ F, gain=5dB +0 L Frequency Response V DD=5V, R L=4 Ω , C IN=1 μ F +25 G0=1 G1=1 +22.5 -10 -20 +20 -30 +17.5 d +15 B r +12.5 A G0= 0 G1=1 R -40 d B G0=1 G1= 0 -50 -60 +10 -70 +7.5 G0= 0 G1= 0 +5 L -80 +2.5 -90 +0 20 50 100 200 500 1k 2k 5k 10 k -100 20 20k 50 100 200 500 1k 2k 5k Hz Hz Noise Floor FFT Inputs ac-ground, V DD=5V, C IN=1 μ F, R L=4 Ω , Gain=23dB -50 Crosstalk vs Frequency V DD=5V, R L=4 Ω , Gain=23dB -50 -55 -60 -60 R to L -70 -65 R -80 -70 d B -75 d B r -80 A -90 -100 -85 L to R -110 -90 -120 -95 -100 20 50 100 200 500 1k 2k 5k 10k -130 20 20k L 50 100 200 500 1k 2k 5k 10 k 20 k Hz Hz Power Analog Microelectronics , Inc www.poweranalog.com 03/2009 Rev 1.1 11 PAM8404 3W/CH Filterless Stereo Class-D Audio Amplifier Typical Operating Characteristics (T =25°C) A WCPS 2x2-16 Quiescent Current vs Supply Voltage No Input, R L=No Load Frequency vs Supply Voltage Input ac-ground 16 304 300 12 Frequency(KHz) Quiescent Current(mA) 14 10 8 6 4 296 292 288 2 0 284 2 2.5 3 3.5 4 4.5 5 5.5 6 2 2.5 3 Output Power vs Supply Voltage C IN=1 μ F, R L=8 Ω , Gain=23dB, f=1kHz 3 4.5 5 5.5 6 5.5 6 Output Power vs Supply Voltage C IN=1 μ F, R L=4 Ω , Gain=23dB, f=1kHz 2.5 Output Power(w) 1.6 Output Power(w) 4 Pow er Supply Voltage(V) Pow er Supply Voltage(V) 2 3.5 10% 1.2 0.8 1% 0.4 2 10% 1.5 1 1% 0.5 0 0 2 2.5 3 3.5 4 4.5 5 5.5 6 2 Pow er Supply Voltage(V) 2.5 3 3.5 4 4.5 5 Pow er Supply Voltage(V) Power Analog Microelectronics , Inc www.poweranalog.com 03/2009 Rev 1.1 12 PAM8404 3W/CH Filterless Stereo Class-D Audio Amplifier Test Setup for Performance Testing PAM8404 Demo Board Load +OUT AP System One Generator Input AP Low Pass Filter GND -OUT AP System One Analyzer AUX-0025 VDD Power Supply Notes 1. The AP AUX-0025 low pass filter is necessary for class-D amplifier measurement with AP analyzer. 2. Two 22μH inductors are used in series with load resistor to emulate the small speaker for efficiency measurement. Power Analog Microelectronics , Inc www.poweranalog.com 03/2009 Rev 1.1 13 PAM8404 3W/CH Filterless Stereo Class-D Audio Amplifier Application Information Gain Settin For this reason, a low-leakage tantalum or ceramic capacitor is the best choice. When polarized capacitors are used, the positive side of the capacitor should face the amplifier input in most applications as the DC level is held at V DD/2, which is likely higher than the source DC level. Please note that it is important to confirm the capacitor polarity in the application. The gain of PAM8404 can be selected as 6,12,18 or 24 dB utilizing the G0 and G1 gain setting pins. The gains showed in the following table are realized by changing the input resistors inside the amplifier. The input impedance changes with the gain setting. 0 0 2 6 28.1 If the corner frequency is within the audio band, the capacitors should have a tolerance ±10% or better, because any mismatch in capacitance cause an impedance mismatch at the corner frequency and below. 0 1 4 12 17.3 Decoupling Capacitor (CS) 1 0 8 18 9.8 1 1 16 24 5.2 Table-1: Gain Setting G1 G0 GAIN GAIN INPUT IMPEDANCE (V/V) (dB) (kΩ) The PAM8404 is a high-performance CMOS audio amplifier that requires adequate power supply decoupling to ensure the output total harmonic distortion (THD) as low as possible. Power supply decoupling also prevents the oscillations causing by long lead length between the amplifier and the speaker. For optimal performance the gain should be set to 2x (Ri=150k Ω ). Lower gain allows the PAM8404 to operate at its best, and keeps a high voltage at the input making the inputs less susceptible to noise. In addition to these features, lower value of Gain minimizes pop noise. The optimum decoupling is achieved by using two different types of capacitors that target on different types of noise on the power supply leads. For higher frequency transients, spikes, or digital hash on the line, a good low equivalentseries-resistan ce (ESR) ceramic capacitor, typically 1μF, is placed as close as possible to the device each VDD and PVDD pin for the best operation. For filtering lower frequency noise signals, a large ceramic capacitor of 10μF or greater placed near the audio power ampl ifier is recommended. Input Capacitors (Ci ) In the typical application, an input capacitor, Ci, is required to allow the amplifier to bias the input signal to the proper DC level for optimum operation. In this case, Ci and the input impedance Ri form a high-pass filter with the corner frequency determined by the follow equation: 1 fC = (2p RiCi) How to Reduce EMI It is important to consider the value of Ci as it directly affects the low frequency performance of the circuit. When Ri is 28.1kΩ and the specification calls for a flat bass response are down to 200Hz, the equation is reconfigured as follows: 1 Ci = (2p Rifc ) Most applications require a ferrite bead filter for EMI elimination as shown at Figure 1. The ferrite filter reduces EMI of around 1MHz and higher. When selecting a ferrite bead, choose one with high impedance at high frequencies and low impedance at low frequencies. Ferrite Bead OUT+ When input resistance variation is considered, the Ci is 28nF, so one would likely choose a value of 33nF. A further consideration for this capacitor is the leakage path from the input source through the input network (Ci, Ri + Rf) to the load. This leakage current creates a DC offset voltage at the input to the amplifier that reduces useful headroom, especially in high gain applications. 220pF Ferrite Bead OUT220pF Figure 1: Ferrite Bead Filter to Reduce EMI Power Analog Microelectronics , Inc www.poweranalog.com 03/2009 Rev 1.1 14 PAM8404 3W/CH Filterless Stereo Class-D Audio Amplifier Shutdown operation PCB Layout Guidelines In order to reduce power consumption while not in use, the PAM8404 contains shutdown circuitry to turn off the amplifier's bias circuitry. It features independent shutdown controls for each channel. This shutdown turns the amplifier off when logic low is placed on the SDx pin. By switching the shutdown pin to GND, the PAM8404 supply current draw will be minimized in idle mode. Grounding It is recommended to use plane grounding or separate grounds. Do not use one line connecting power GND and analog GND. Noise currents in the output power stage need to be returned to output noise ground and nowhere else. When these currents circulate elsewhere, they may get into the power supply, or the signal ground, etc, even worse, they may form a loop and radiate noise. Any of these instances results in degraded amplifier performance. The output noise ground that the logical returns for the output noise currents associated with class D switching must tie to system ground at the power exclusively. Signal currents for the inputs, reference need to be returned to quite ground. This ground only ties to the signal components and the GND pin. GND then ties to system ground. Short Circuit Protection (SCP) The PAM8404 has short circuit protection circuitry on the outputs to prevent the device from damage when output-to-output shorts or output-to-GND shorts occur. When a short circuit occurs, the device immediately goes into shutdown state. Once the short is removed, the device will be reactivated. Over Temperature Protection (OTP) Power Supply Line Thermal protection on the PAM8404 prevents the device from damage when the internal die temperature exceeds 150°C. There is a 15°C tolerance on this trip point from device to device. Once the die temperature exceeds the set point, the device will enter the shutdown state and the outputs are disabled. This is not a latched fault. The thermal fault is cleared once the temperature of the die decreased by 50°C. This large hysteresis will prevent motor boating sound well and the device begins normal operation at this point with no external system interaction. Same a s the ground, VDD and PVDD need to be separately connected to the system power supply. It is recommended that all the trace could be routed as short and thick as possible. For the power line layout, just imagine water stream, any barricade placed in the trace (shown in figure 2) could result in the bad performance of the amplifier. POP and Click Circuitry Figure 2: Power Line The PAM8404 contains circuitry to minimize turnon and turn-off transients or “click and pops”, where turn-on refers to either power supply turnon or device recover from shutdown mode. When the device is turned on, the amplifiers are internally muted. An internal current source ramps up the internal reference voltage. The device will remain in mute mode until the reference voltage reach half supply voltage V DD/2. As soon as the reference voltage is stable, the device will begin full operation. For the best power-off pop performance, the amplifier should be set in shutdown mode prior to removing the power supply voltage. Components Placement Decoupling capacitors-As previously described, the high-frequency 1μF decoupling capacitors should be placed as close to the power supply terminals (VDD and PVDD) as possible. Large bulk power supply decoupling capacitors (10μF or greater) should be placed near the PAM8 404 on the PVDD terminal. Input capacitors need to be placed very close to input pins. Output filter - The ferrite EMI filter should be placed as close to the output terminals as possible for the best EMI performance, and the capacitors used in the filters should be grounded to system ground. Power Analog Microelectronics , Inc www.poweranalog.com 03/2009 Rev 1.1 15 PAM8404 3W/CH Filterless Stereo Class-D Audio Amplifier Ordering Information PAM8404 X X X Shipping Package (R: Tape & Reel) Number of Pins (E: 16; G: 20) Package Type (Z: WCSP; K: QFN4x4) Part Number PAM8404ZER PAM8404KGR Marking FR YW P8404 XXXYW Package Type Shipping Package WCSP 16 3,000 Units/Tape & Reel QFN4x4 20L 3,000 Units/Tape & Reel Power Analog Microelectronics , Inc www.poweranalog.com 03/2009 Rev 1.1 16 PAM8404 3W/CH Filterless Stereo Class-D Audio Amplifier Outline Dimensions WCSP 2x2 1.00 1.95 ± 0.02 0.50 1.95 ± 0.02 Units:Millimeter 0.235 ± 0.02 0.415 ± 0.04 Power Analog Microelectronics , Inc www.poweranalog.com 03/2009 Rev 1.1 17 PAM8404 3W/CH Filterless Stereo Class-D Audio Amplifier Outline Dimensions QFN4x4-20L Power Analog Microelectronics , Inc www.poweranalog.com 03/2009 Rev 1.1 18